Cary Institute visitors often encounter researchers in white coveralls. Their suits help prevent unwanted tick bites while they investigate the ecological conditions that regulate Lyme disease risk. As human populations move into suburban and rural environments, encounters with infected black-legged ticks have increased. In the Northeast, Dutchess County has one of the highest human infection rates.
Research conducted at the Cary Institute has correlated the prevalence of infected black-legged ticks with land use and biodiversity loss. When the landscape is highly fragmented and white-footed mice dominate, human risk increases. In intact landscapes with a diversity of animals, such as opossum and fox, human risk declines. This is because non-mouse hosts are less likely to transfer Lyme disease to ticks.
An analogous finding is seen in West Nile virus research. Infection is most common in developed areas, where blue jays and crows dominate local bird populations (the virus is amplified in their bodies). In less developed areas, where the native bird fauna is more diverse, human risk decreases.
The “dilution effect” has applications to other infectious disease systems and highlights the importance of species protection in land-use planning.